The Robot Workbench is unmaintained. If you have experience with the topic and are interested in maintaining it, please state your intention in the developer's section of the FreeCAD forum.

The reason this workbench is still in the master source code is because this workbench is programmed in C++. If this workbench could be programmed in Python, then it could be made an external workbench and it could be moved to a separate repository.